Peroxygen bleach-containing compositions have been extensively described in laundry applications as laundry detergents, laundry additives or even laundry pretreaters.
Indeed, it is known to use such liquid peroxygen bleach-containing compositions in laundry pretreatment applications to boost the removal of encrustated stains/soils which are otherwise particularly difficult to remove such as grease, coffee, tea, grass, mud/clay-containing soils and the like. However, a drawback associated with such liquid peroxygen bleach-containing compositions is the relative instability of said compositions. Indeed, such liquid peroxygen bleach-containing compositions when packaged in containers made out of deformable materials, typically thermoplastic materials, may cause so-called bulging problems. The peroxide bleach in the composition decomposes with time so as to generate oxygen in the composition. The released oxygen builds up pressure inside the container which eventually deforms, i.e., bulges. The rate of decomposition of peroxygen bleach depends on different parameters such as temperature, pH and/or presence of metal ions.
Known solutions to this problem are to use in such peroxygen bleach-containing compositions metal ions chelating agents, e.g., polyaminocarboxylates and/or phosphonate chelating agents, and/or radical scavengers which contribute to reduce peroxygen bleach decomposition and thus to stabilise said compositions.
Representative of the art is for example, EP-B- 209 228, which discloses the use of metal ions chelating agents such as amino polyphosphonates and radical scavengers such as hydroxybenzene compounds (butylated hydroxy toluene) to stabilise liquid hydrogen peroxide bleaching compositions.
However, such liquid peroxygen bleach-containing compositions are not totally satisfactory from a formulator point of view as said compositions all the same tend to be somewhat chemically unstable and consequently all the same tend to bulge the containers into which they may be packaged. In other words, it has been found that there is still room for further improving the chemical stability of a liquid peroxygen bleach-containing composition.
It is thus an object of the present invention to formulate liquid peroxygen bleach-containing compositions which exhibit improved chemical stability, especially upon prolonged periods of time.
It is further desirable when formulating peroxygen bleach-containing compositions suitable to be used as pretreater, that said compositions are safe to said fabric treated therewith. Indeed, it has been found that a drawback associated with such peroxygen bleach-containing compositions is that said compositions may damage fabrics, resulting in loss of tensile strength of the fabric fibres and/or color damage, when used in pretreatment application under stressed conditions, e.g., when applied directly onto the fabrics, and left to act onto said fabrics for prolonged periods of time, i. e., several hours, before washing said fabrics and/or when the fabrics to be pretreated are contaminated with metal ions such as copper and/or iron and/or manganese and/or chromium. Indeed, it is speculated that the presence of metal ions such as copper and/or iron and/or manganese and/or chromium on the surface of the fabrics, especially on cellulosic fibres, catalyses the radical decomposition of peroxygen bleaches like hydrogen peroxide. Thus, it is believed that a radical reaction occurs on the surface of the fabric with generation of free radicals, which results in tensile strength loss. Furthermore, it is speculated that this generation of free radicals may further provide an aggressive decomposition of certain dyes present in the fabrics resulting thereby in chemical damage of dye molecules which is visible as discoloration and/or hue change. Dyes commonly present in colored fabrics include metal containing dyes like copper-formazan dyes or metal-azo dyes.
Therefore we have found essential that this surface reaction resulting in generation of free radicals is controlled in the pretreatment environment, thereby providing improved safety to fabrics and colors.
It has now been found that this can be achieved by adding to a peroxygen bleach-containing composition a specific polyamine or mixtures thereof. Indeed, it has been unexpectedly found that the addition of a polyamine as defined hereinafter, or mixtures thereof, allows to dramatically reduce the decomposition of peroxygen bleaches like hydrogen peroxide, even under stressed conditions like prolonged exposure at high temperature, for example at 50.degree. C. during 20 days. More particularly, it has been found that the use of said polyamine, or mixtures thereof, in a peroxygen bleach-containing composition, delivers improved chemical stability to said composition as well as improved fabric safety and/or improved color safety to fabrics pretreated with said composition, this both when used alone or in combination with other bleach stabilisers like chelating agents and/or radical scavengers. Indeed, it is believed that this stabilising effect and fabric safety properties are matrix independent.
Actually, there is an optimum concentration for each of the chelating agents and/or radical scavengers used in peroxygen bleach-containing compositions which delivers the maximum benefits in terms of peroxygen bleach stability. For example in a peroxygen bleach-containing composition comprising about 10% by weight of peroxygen bleach or less, the optimum concentration of a well-known chelating agent like s,s, ethylenediamine N,N'-disuccinic acids (ssEDDS), or diethylene triamine pentamethylene phosphonates or diethylene triamine pentaacetates (DTPA) is around 0.01% to 0.3% by weight of the total composition of said chelating agent. In other words, it has been observed that by further increasing the optimum concentration for peroxygen bleach stability of said chelating agent in a peroxygen bleach-containing composition, said composition becomes less chemically stable, i.e. the peroxygen bleach decomposition increases. Additionally, it has been observed that by combining different chelating agents at their optimum concentration for peroxygen bleach stability, the peroxygen stability does not increase on the contrary such combinations usually contribute to decreasing the peroxygen stability. It has now unexpectedly been found that the present invention allows to use a specific polyamine, or mixtures thereof, in combination with other bleach stabilizer like chelating agents and/or radical scavengers and to provide thereby peroxygen bleach compositions with improved chemical stability.
An advantage of the present invention is that excellent laundry performance on a broad range of stains and soils such as bleachable stains and/or greasy stains.
Another advantage of the present invention is that the compositions of the present invention provide also excellent performance when used in other applications, apart from laundry pretreater application, such as in other laundry applications, as a laundry detergent or laundry additive, or even in hard surface cleaning applications or in carpet cleaning applications.